I suspect there is a critical mass point that once achieved turns a peaceful protest into a violent mob that is difficult to deal with.
The mounted officers and officers on bikes in the video would have had their hands full in Portlandia. The local goons know how to take on the horse patrol, and know that a large mob makes it difficult to effectively control. They were quite effective against a small, apparently peaceful group.
The locals yelling at them to get out of town is something just not seen in Portlandia. A few hardy souls have tried to counter-protest, but have been surrounded by the mob right in front of cops then hustled a few yards away to be beaten. While the cops do nothing. And those waiting for the balloon to go up have chosen to avoid areas like Portlandia mobs control. It's not the ground they've chosen to make their stand on. Better to let the mob destroy liberal land and be contained there rather than see it spread to suburbs or rural areas.
Having said that, it does give a warm feeling to see the heartland doing what big blue cities should have done. Nip it in the bud and show decisively who is in charge.